The Ammonites (Speetoniceras versicolor) - (Reference|Index} Fossils



Ammonites have been known to mankind for thousands of years. They are the source of lots of stories and misconceptions. The name of this spiral-shelled cephalopod originates from the Egyptian god Ammon. Ammon was pictured as a man with the horns of a ram extending from his head. The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites. Ammonites have actually been known to mankind for thousands of years. The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.

Ammonite Myths
Lots of cultures throughout history have attributed unique powers to this fossil.

In ancient Greece, it was stated that if you put an ammonite under your pillow it would cure insomnia and bring excellent dreams.

The Romans thought that if you put a golden ammonite (pryritized) under your pillow you would have prophetic dreams.

A Brief History of Ammonites
Ammonites initially appeared in the Devonian Period. Ammonites of later periods developed septa that had complex folds called saddles and lobes. Ammonites such as Russian Speetoniceras are very attractive often on auction.

Since all living cephalopods (octopus, nautilus, and squid) are predators, we can assume that ammonites were. The only living cephalopod with an external shell is the chambered nautilus. It can swim and control its depth. It does this using the siphuncle. The siphuncle is a tube that links all the chambers in the shell with the living animal. The nautilus can add or read more deduct gas in these chambers to manage buoyancy.

Ammonite Size
Ammonites internet have a large range of size. Specimens have been discovered ranging from less than a centimeter to 2 meters in diameter. Early ammonites, up until the middle Jurassic, were smaller sized, normally less than 9 inches or 23 centimeters. During the upper Jurassic and lower Cretaceous larger varieties can be found. Titanites discovered in the south of England can be over 50 centimeters, 2 feet in diameter.

Biostratigraphy
The hard shell of the ammonite was easily fossilized. This, integrated with the sheer abundance of this group of cephalopods and its evolutionary period through a number of geologic durations, make it an excellent index fossil. Index fossils assist geologists and paleontologists to figure out the age of rock layers. This is called biostratigraphy. It works like this. The rock layer it came from should be Triassic if you find an ammonite from a genus understood to be from the Triassic Period. To be an excellent index fossil:

It needs to have large circulation.

There must be a great deal of them.

It needs to belong to a group that evolves quickly.

They should be easy to acknowledge.

Ammonites please all of the above requirements easily.

Extinction of The Ammonites
The end of the Cretaceous Period was also completion of the ammonites. This was about 65 million years ago. Dinosaurs and lots of other species of plants and animals passed away out at about this very same time. It is believed that a huge meteor hitting earth caused these mass terminations.

The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.

Ammonites of later periods established septa that had actually complex folds called saddles and lobes. The hard shell of the ammonite was quickly fossilized. If you find an ammonite from a genus understood to be from the Triassic Period, then the rock layer it came from should be Triassic. The end of the Cretaceous Period was likewise the end of the ammonites.

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